In 2000, the National Highway Traffic Safety Administration (NHSTA) required automobile manufacturers to recall thousands of tires because of accidents allegedly resulting from tire tread separation. Suspect tires were traced back through the tire manufacturer's quality records. However, no records existed in the vehicle chassis assembly process to link tires' serial numbers to the vehicle identification number (VIN). Legislation passed by Congress and the Department of Transportation now requires automobile manufacturers to implement a tracking system to link the tires' serial numbers and VIN. Additionally, tire and automobile manufacturers have been encouraged to implement a more reliable and accurate method of tracking the DOT code, tire serial numbers, size, type, date, manufacturing plant, and mold machine for every tire and to tie this information to the VIN.
The tire recalls were massive because no data existed as to which tire lots and/or tire manufacturing dates had been installed on specific vehicles. Tire manufacturers had been relying upon hand stamping tires with lot and date codes using indelible ink or using raised bar code symbols directly embossed or molded into the surface of a tire to track and identify tires. However, the low data density of these systems prevented them from incorporating the required data storage volume. The molding technology increased tire manufacturing costs while limiting flexibility for incorporating on-demand variable data.
Other technologies providing high-density machine readable data include U.S. Pat. No. 4,991,217 which describes a passive radio frequency identification transponder tag which is interrogated by a radio frequency field from outside of the tire. This radio frequency identification is susceptible to radio wave interference and damage from vulcanization heat/pressure during the tire's manufacturing/tag mounting process.
U.S. Pat. No. 5,160,383 discloses a tire label permanently mounted to an inner liner of the tire for tracking of the tire's serial numbers throughout the entire life of the tire up to and including retreading of the tire. The label is manufactured using a SPBD/rubber blend which is permanently affixed to the inside of the tire where it is cured along with the tire in a mold by the heat and pressure of the vulcanization curing process. Mounted on the inside of the tire, the label is only readable when the tire casing has been removed from the tire rim. U.S. Pat. No. 4,010,354 discloses a magnetically encodable tag in a sequential tape format that is encoded with tire's identifying data which is applied to the side wall material of a green tire. The magnetically encoded tape and associated encoding and decoding equipment increase the tire costs.
The use of magnetically encodable tags in tape format written sequentially with tire identifying data and applied to the sidewall material of a green tire is described in U.S. Pat. No. 4,010,354. The encoded data is readable from the tire at any point in the tire's manufacturing process and the signals indicative of the tire's identification number are converted to an alphanumeric display and/or fed to a process control computer for on-line quality assurance and control or stored as a recorded history of the tire manufacturing process for inventory control.
The use of a resin based film type substrate used for a tire's production control label is described in U.S. Pat. No. 5,709,918. The label surface is printed with a bar code and a pressure sensitive adhesive layer is formed via a primer layer on the back side of the label surface. The printing does not become blurred or erased under the high temperatures and high pressures during vulcanization.
An apparatus and method for supplying a graphic label that is readable with a light scanning device when the label placed on a rubber article such as a tire is described in U.S. Pat. No. 5,527,407. The graphic bar code label is optically interpreted by a bar code reader. Printing is applied using thermal transfer techniques.
A label is designed to be disposed on an unvulcanized raw rubber tire and then fixed to the finished tire by vulcanization using heat and pressure is described in U.S. Pat. No. 5,358,772. The indication label has a label base material with a heat-resistant plastic film and an abrasive surface coating layer formed on the upper surface of the plastic film. The abrasive surface includes a hardened resin and filler. An indication defined by an ink layer is disposed on the abrasive surface. A rubber adhesive laminated on the lower surface of the plastic film adheres the label to the tire. The label is constructed by forming the ink layer on the exterior side of the abrasive surface coating layer. The abrasive surface has a profile and roughness for preserving the quality of the indication.
Current label designs for labeling tires use conformable films such as biaxially oriented polypropylene (BOPP) or polyolefins (blends of polypropylene and polyethylene) for the label face stock. These films conform well to a tire surface, but as the tire ages there are components within the rubber compounds that bleed and migrate to the surface and interact with the label's film. Migration is also a problem for tires exposed to elevated temperatures, for example within a trailer during storage/transportation during summer months. This migration of waxes, oils, lubricants, plasticizers and other low molecular weight additives into the label adhesive and label film not only discolors the label but also impacts the adhesive bond of the label film, making it weaker and likely to lift or flag.